sql语句将字符串转换为数字默认去掉单引号中的空格，遇到空格作为字符串截止，

 '123 and 1=1' 0

结果为123

 

里面如何用sql语句让字符串的‘123’转换为数字的123？

方法一：SELECT CAST('123' AS SIGNED integer);

方法二：SELECT CONVERT('123',SIGNED);

方法三：SELECT '123'+0;

 

同样，当需要将一列字符串转换为数字也可以使用此方法，或者需要用到字符串进行排序的时候可以使用到此方法：

 

SELECT * FROM answer WHERE question_id = xx ORDER BY CONVERT(`code`,SIGNED)

 

               SELECT * FROM answer WHERE question_id = xx ORDER BY cast(`code` as signed integer)
SELECT * FROM answer WHERE question_id = xx ORDER BY cast(`code` as signed integer)